A botnet is made up of any number and type of Internet-connected devices that are running bots. Typically, the botnet includes various computers and other devices that have infected with malware. The master of the botnet controls the botnet remotely by communicating with the infected devices using command and control software. The command and control software can be hosted on botnet domains that the master of the botnet uses to establish communication channels with the infected devices and send commands to remotely control the infected devices of the botnet.
One tool used by botnet masters to create botnet domains is domain generation algorithms (DGA). Using DGA, an infected device can periodically generate a large number of domain names that can be used to establish communication with command and control software. The large number of potential domains generated by DGA makes it difficult to shut down the botnet and sever the communication link between the botnet and the command and control software.